Inflammatory bowel disease has more than one pathogenesis. One of these involves an immune response, mediated by lymphocytes, against antigens of the colon. This response leads to the accumulation of inflammatory cells in the colon and alteration of the surface epithelium. The specific class of lymphocytes which produce this damage is being investigated by transferring lymphocytes from immune to normal rats. Both T and B lymphocytes will be isolated and transferred. In lymphocyte recipients who develop the disease the therapeutic effect of Tor B lymphocyte depletion will be studied. Suppressor lymphoctes to colon specific antigen will be induced by immunization with colon antigen in incomplete Freund's adjuvant. The effect of the suppressor lymphocytes on modifying the disease process in animals with active disease will be studied. Preliminary studies have indicated that anti colon antibody may interfere with the cytotoxic activity of lymphocytes reactive to colon antigen. This observation will be pursued.